This is one of my favourite projects to date.

Take one standard 2001 Subaru Impreza WRX, take one drivers club called the Subaru Impreza Drivers Club (SIDC) and one website called eBay. And what do you get? 

A Subaru Impreza WRX PPP for the fraction of a cost of what you’d pay for PPP form a dealer!  Just in case your wondering, PPP isn’t the latest drug..  Well maybe it is.. it stands for Prodrive Performance Pack.  Prodrive is the UK company based in Banbury who have run the Subaru World Rally Team for many years now. They know Subaru’s inside and out, and it shows. The PPP makes for a more powerful, more torquey and a much more driveable car!!

Here’s how I managed to upgrade to PPP for under £320! (RRP £1,500)

So what’s it all about.. The Prodrive Performance Pack consists of ECU upgrade / removal of the 3rd catalytic converter. New burbly backbox and a stronger silicone pipe for the turbo.. Standard one is hardened plastic and was known to go *POP* when the higher boost levels were applied.

Ok time to take a count..  RRP of a Prodrive Performance Pack for my car? £1,500 And how much did it cost me?

  • Prodrve backbox off eBay – £129
  • Prodrive 3rd cat delete pipe from a member of the SIDC – £55
  • Silicone y-pipe between turbo and intercooler , ebay again – £42.01
  • ECU Upgrade – £87.19 (ODB-II cable from tactrix in the USA) 
  • Total cost: £ 313.20

In fairness I’m still using the standard WRX ECU but it’s got a performance map “based” on the newer 265bhp PPP map which can be found on the 2003 model WRX.  Which in theory makes this more powerful than the original PPP for my car  yeeHaa!! (Origonal PPP took power to just 245bhp from the standard 215bhp)

So count all that up and you see I had a saving of £1,186.80 over RRP!  Well worth it! Also worth noting that the parts were installed by me! Not a garage so no labour costs. I like getting my hands dirty with this and it feels better to do it yourself and see the rewards!

Installing the parts was simple enough.. but the ECU map was a little different.. the £87 comes from the cost of getting a ECU->USB cable imported from the USA (including £23 to get it through customs).  This cable allowed me to plug a laptop, or any other PC, into the car’s ECU. After that it was simply a case of runnign some tests monitoring air flows and ignition timings tweaking the map step by step to be as close as possible to the prodrive spec. Then finally makign adjustments for the way I wanted the car to respond to the throttle.

Ok admit this sounds easy. In fairness it too a hell of a lot of research and learning to understand the maps what to do and making sure I understood what each change to the ECU map meant for the engine before changing anything. One wrong value and you could kill the car easily!

Even after I managed to get the new map and performing similarly to a WRX with PPP. I felt I could fiddle with the map to get the car performing the way I wanted it to. So  I tweaked it a bit more so the boost comes in earlier and harder across the rev range.  Sadly due to the limitations of the TD04 turbo the boost needs to be tailed off after 5,000rpm otherwise the turbo potentially overheats and turns into a flamethrower! BTW – No matter how “cool” that sounds. It’s not a good thing!

As part of the remap a lot of data logging took place and although the map was doing everything it should. I originally wasn’t getting the boost required from the turbo. Only 1.02 bar from the standard 0.9 bar a difference was felt in driving but not the neck braking acceleration I had hoped for.  Again after some more research, this time into the specification of the Turbo I discovered that it was capable of producing around 1.3bar of boost before things start going wrong.. After much testing I traced the problem down to the wastegate arm on the turbo not stayign closed and allowing air to bypass the turbo. It was basically doing it’s job!. So pulled the turbo heatshield off, tightened up the wastegate arm a couple of turns, put it all back together and did some more testing. 

That did the trick!  Turbo now boosting at 1.2bar at under 3,000RPM and pulling a strong 1.29bar all the way up to 5,000 and my god can you feel the difference!  Welly it in a low gear and not even the permanent 4wd system can keep traction on a damp road surface! Not the sort of performance to be messed around with! In the dry the thing just takes off like a rocket (assuming the clutch, driveshaft’s and gearbox don’t break)..

Note: Most of this project took place over several months during 2007.. But from the point of starting the research it took nearly 11 months just to get an understanding of what I was doing. And I’m not finished. There’s still a couple things that need to be worked out of the map..

There really isn’t much that could keep up with a well sorted Impreza!!